The present invention relates to a measuring instrument such as a pH meter, an ion meter or a conductivity meter, provided with measuring electrodes which are either releasably connected to an instrument body via a cable or are made wireless-communicable. More particularly, the present invention relates to a very useful measuring instrument having measuring electrodes equipped with storage means (memory) in which information regarding the properties of the measuring electrodes is input, or having identification means for identifying the measuring electrodes, provided in the measuring electrodes, and storage means (memory) for identifying the measuring electrodes and storing information regarding the measuring electrodes provided in the instrument body.
For example, in a measuring instrument such as a pH meter or an ion meter releasably connected to an instrument body via a cable, or provided with measuring electrodes made wireless-communicable, it is currently common practice to calibrate the properties of each electrode by using a standard solution before actual use, and to calculate, correct and display a measured value on the basis of the calibration data. For an electrode requiring a correction value as in a conductivity meter or a conductivity cell, it is required to visually read out the correction value displayed on the electrode and set the correction value on the instrument body before use. For electrode control purposes, it is necessary to record the model and the manufacture No. of the electrode.
As described above, therefore, while data calibrated upon use of an electrode or the correction value is stored in the memory, in a conventional measuring instrument, it is necessary, when replacing the electrode with another one, to perform the calibration over again with a standard solution for the new electrode, or set a new correction value.
In some measuring instruments, several calibration values are stored and can be selectively employed. Even in this case, the operator has to remember what part of the stored data corresponds to which of the electrodes so as to select an appropriate electrode by key operation before use. Another problem is that failure to select the correct calibration value means that the measurement will be done on the basis of wrong data. The model and manufacture No. indicated on the electrode label has to be noted down. The instrument body can not automatically identify an electrode.
In an electrode requiring a correction value such as a conductivity cell, a cell constant must be set in the instrument body, as described above. A conductivity cell has electrodes of different shapes, and upon every replacement of an electrode, a cell constant must be set. An accurate measurement can therefore be hindered by an erroneous setting or failure to set correctly. Further, a printout of the result of measurement contains only the result of measurement, without any printed information indicating the electrode for which the result has been obtained.